How can `D_(2)O_(2)` prepared form water ? Mention the physcial properties in which `D_(2)O` differs from `H_(2)O`. Given at least three reaction of `D_(2)O` showing the exchange of hydrogen with deuterium.

Explanation

### Step-by-Step Solution

**Step 1: Preparation of D₂O from Water**

D₂O, also known as heavy water, can be prepared from regular water (H₂O) through the process of prolonged electrolysis. In this method, water is subjected to electrolysis, which separates the components based on their isotopic differences. Deuterium, being heavier than protium (the most common hydrogen isotope), accumulates in the electrolytic cell, allowing for the collection of D₂O.

**Reaction:**
\[ 2H_2O \rightarrow 2H_2 + O_2 \]
During this process, the deuterium in the water gets concentrated, leading to the formation of heavy water.

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**Step 2: Physical Properties of D₂O vs. H₂O**

D₂O differs from H₂O in several physical properties:

1. **Density**:
- D₂O has a maximum density of approximately 1.1073 g/cm³.
- H₂O has a maximum density of about 1 g/cm³.

2. **Viscosity**:
- The viscosity of D₂O is greater than that of H₂O, making it more resistant to flow.

3. **Melting and Boiling Points**:
- D₂O has higher melting and boiling points compared to H₂O.
- The melting point of D₂O is about 3.82 °C, while that of H₂O is 0 °C.
- The boiling point of D₂O is approximately 101.4 °C, whereas H₂O boils at 100 °C.

4. **Stability**:
- D₂O is relatively unstable and can decompose to form H₂O and oxygen under certain conditions.

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**Step 3: Reactions Showing Exchange of Hydrogen with Deuterium**

Here are three reactions that illustrate the exchange of hydrogen with deuterium:

1. **Reaction with Sodium Hydroxide**:
\[ \text{NaOH} + \text{D}_2\text{O} \rightarrow \text{NaOD} + \text{HOD} \]
In this reaction, sodium hydroxide reacts with heavy water, resulting in the formation of sodium deuteroxide and hydrogen deuteroxide.

2. **Reaction with Hydrochloric Acid**:
\[ \text{HCl} + \text{D}_2\text{O} \rightarrow \text{DCl} + \text{HOD} \]
Here, hydrochloric acid reacts with heavy water to produce deuterium chloride and hydrogen deuteroxide.

3. **Reaction with Ammonium Chloride**:
\[ \text{NH}_4\text{Cl} + \text{D}_2\text{O} \rightarrow \text{NH}_3\text{DCl} + \text{HOD} \]
In this reaction, ammonium chloride reacts with heavy water to yield deuterated ammonia and hydrogen deuteroxide.

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